The table below lists the commands for clearing the DNS cache on most macOS and Mac OS X versions. For example: sudo killall -HUP mDNSResponder say dns cleared successfully Flush DNS Commands on Older macOS and Mac OS X Versions Note: If you want to hear an audio notification after the DNS flush is complete, type say some text after the first command. Ps: Hannes, it seems format filters are not run through comments, even using p tags. I'm not expert at bash scripting, so if anyone could improve this script to dynamically retrieve the Network Service to reset, it would be nice Note that /Network/Service/87FB33AE-EEBD-4675-A4FC-7BB0E576BC90/DNS is specific to my Network Service Here are the needed lines to be executed within scutil, stored in /etc/ppp/scutil_session.txt # Here I create my routes using /sbin/route add. # $6 the parameter specified by the 'ipparam' option to pppd # $4 the local IP address for the interface # $1 the interface name used by pppd (e.g.
# When the ppp link comes up, this script is called with the following
#What dns servers mac manual#
Either that or doing manual DNS entries for the VPN setup that include the remote DNS and local DNS, then you don't need to run the script at all.įollowing my previous comment, I'd like to share the script I added when the ppp connection goes up so this scutil session can be done automatically.Ĭreate the following script as root /etc/ppp/ip-up and make it executable:
While I haven't tried it yet, I presume a similar script to *add* local DNS servers to the list when connected would work. Using the raw solution here would just make me lose the ability to resolve internal hosts on the VPN. This completely breaks the standards for DNS where it would and should fall back to the other listed DNS servers to try when earlier ones fail to resolve. If the local network uses split horizon, ie: internal DNS that lists hosts that don't need to be resolved externally, you lose that when you connect the vpn because you lose the internal DNS server for your local network.įor instance, when I connect to my home office VPN, I can resolve the internal ip addresses there fine (and external ip addresses work fine), however I lose the ability to resolve the internal ip addresses at our main office, so my email, bug tracking, call management and pretty much everything else that depends on DNS goes away. It isn't just vpn's managed by an operator from hell. It would be fairly straight-forward to script the above scutil session but you'd still have to run the script manually after a network connection comes up. If you want to specify particular DNS servers, useĭ.add ServerAddresses * 10.0.1.2 112.21.44.66īy the way, the "*" signifies array values, so it's not some kind of wild card.Ĭheck the Networking Preference panel and you will notice those damn grayed out DNS server entries are gone! They will come back next time you connect and they will be first in the list. Without service-specific DNS servers, Mac OS will fall back to DNS servers from other network services. > set State:/Network/Service/A3551F2D-62CE-1234-B79A-6EE50CA7AE30/DNSĬlears the ServerAddresses array, thereby removing all DNS-servers tied to that particular connection ("service" in Apple-talk). Reset the ServerAddresses entry to an empty array:
Obtain a working copy of the DNS configuration entry. > show State:/Network/Service/A3551F2D-62CE-1234-B79A-6EE50CA7AE30/DNSĪhh, this is the one! So let's get rid of those pesky servers. List all network services with DNS configuration: With the VPN connected, launch scutil with root privileges: After hours and hours of hard work (my fingertips still hurt from all the googling) I present to you a solution: For me this need typically arises when I connect to a VPN managed by an operator from hell. Anyways, this would be all swell if there wasn't the occasional need for manually specifying DNS servers. Survival of the fittest, I guess, or, Darwin's intelligent design. They generally go through Darwin's resolver library which instead of reading /etc/nf looks up DNS servers via the SystemConfiguration framework backed by configd. The dig and nslookup utilities still read it but most applications use a different mechanism for picking DNS servers when resolving host names. I'll have to break sad news to you: /etc/nf has been made redundant in Mac OS X.
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